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R.C. Snubber

Product Overview & Application

SNUBBER open FrontR.C. snubbers are a passive electrical devices, comprised of appropriately selected resistors and capacitors, which are used for protecting medium votlage power transformers from electrical switching transients. While lightning arresters help protect the transformers from the high voltage spikes that appear on the line after a lightning strike, snubbers are better suited for the more common problem of circuit breaker switching transients. Examples of the switching operation include instances where a circuit breaker switches between transformer primaries, or automatically triggered switching between grid and reserve power.

When a circuit breaker interrupts current flow, an arc develops across its contacts. The rapid current interruption usually occurs somewhere other than the current zero-crossing point, giving rise to a Transient Recovery Voltage (TRV), which has significant high-frequency content. If the transients are at the natural resonance frequency of the system, then there is a possibility of internal oscillatory voltages developing in the primary windings of the transformer. A high turn-to-turn voltage will result, which will lead to damage of the insulation.

The problem is further exasperated with modern vacuum-type circuit breakers, which have shorter distances between contacts. This serves to increase the speed of the interrupting cycle. The transient level and frequency are functions of the physical distance between the breaker and transformer, transformer construction, the type of load being switched, and the switching characteristic of the breaker.

The RC-snubber network lowers the frequency of the transient voltage applied to the transformer primary below the resonance frequency of the circuit. It reduces the development of the oscillatory voltages and provides a low impedance path to ground for the transients.

Snubbers are a low cost means for protecting a transformer against a costly repair and related downtime. In designing medium voltage power systems, it is a good practice to at least leave space for future installation of a snubber network.

Product Specification

Voltage Class  2.4kV to 34.5kV (150kV BIL)
Frequency  60Hz (50/60Hz Optional)
Fuse  6A Full Range Current Limiting Fuse
Resistor  20 - 50 Ohm (+/- 10%) Tubular Non-Inductive Resistor
Capacitor  0.13uF, 0.25uF, 0.5uF Surge Capacitor
Enclosure Type  Type 1 Indoor
Enclosure Finish  ANSI/ASA 61 Grey
Mounting  Floor Mounting
Warranty  12 Months (See Warranty and Limitations)
Quality System  ISO 9001:2015 Quality Management System
Optional Features & Accessories
  • Snubber Ground Current Monitoring Circuits
  • Distribution, Intermediate or Station Class Surge Arresters
  • Voltage Indicators / Glow Tubes
  • Type 1, 3R or 4X Enclsoure
  • 304 & 316L Stainless Steel Enclosure
  • Custom Enclosure Finish (Color)

Canadian Sales Representatives

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AC Line / Load Reactor

Inductors placed at the input and output of electrical equipment can provide protection and improve performance. Line Reactors absorb many power line disturbances which could damage or shut down your inverters, order variable speed controllers, or other voltage-sensitive equipment.


Read more: AC Line / Load Reactor

General Purpose Isolation Transformer

transformerGeneral Purpose Isolation transformers are used to lower distribution voltages (480 or 600V) to lower voltages (typically 120/240 or 208Y120) for power distribution within commercial or industrial buildings. These “two windings” transformers provide the electrical isolation required, and allow for short runs of high current, low voltage cables, reducing losses in the system, and reducing costs.


Read more: General Purpose Isolation Transformer

Mini Power Center

4-1Rex Power Magnetics Mini Power Centers combine three individual components, prewired into one NEMA 3R enclosure: a primary main breaker, a single-phase or three-phase dry-type encapsulated transformer (Type EP), and a secondary distribution load center with main breaker. Inter-connecting wiring is completed at the factory. Mini Power Centers are used wherever there is a 480V or 600V distribution system and loads requiring 208Y/120V, three-phase or 120/240V single-phase.

Read more: Mini Power Center



Autotransformers are transformers which have a single winding per phase, part of which is common to both primary and secondary circuits. Using an Autotransformer is an economical and compact means of connecting electrical equipment to a power supply or a different voltage. Part of the winding is common to both primary and secondary circuits so there is no isolation between the two. This may be acceptable on some power systems that do not have a grounded neutral on the secondary side of the main power transformer. Typical applications include motor loads of industrial machinery, electric heating, air conditioners, etc. Designed for installation where a reliable power source is required for lighting and other low voltage equipment and machinery. Indoor and outdoor installation is possible depending on the enclosure.

Read more: Autotransformer

Industrial Control Transformer

Industrial control transformers are used to convert the available supply voltage to the voltage that is required to supply industrial control circuits and motor control loads.

These loads consist of a combination of electromagnetic devices such as solenoid operated valves, switches, bells, alarms, and other components such as indicator lights, timers, electronic equipment, and logic boards.

Some components of a circuit, especially electromagnetic devices require a very high level of power at start-up.  This start-up power requirement is called inrush VA. After their initial start-up, these components settle down to a lower power requirement for normal continuous operation. This lower operating power requirement is called Sealed or Steady State VA. Some devices can draw up to 10 times the normal operating or sealed current for periods of up to 50 milliseconds upon start up.

Control transformers must be designed, constructed, and selected to ensure that they provide the output voltage stability needed for trouble free operation of all circuit components.

Rex control transformers incorporate several features to optimize output voltage stability and regulation when supplying industrial control circuits with high inrush current requirements.

Read more: Industrial Control Transformer

Harmonic Mitigating Transformer

Harmonic Mitigating Transformers (HMT's) are specially designed for non-linear loads which draw significant amounts of harmonic current. While K-factor rated transformers are simply designed to handle the additional losses of supplying non-linear loads, HMT's actually minimize the voltage distortion and power losses that result from harmonic load currents.

Read more: Harmonic Mitigating Transformer

Encapsulated Transformer


Encapsulated (Potted) Transformers (also referred to as Epoxy Resin Encapsulated) are designed for applications where the enviromental conditions would not permit a general purpose ventilated dry type transformer. The entire tranformer core & coil is encased in a silica sand / polyurethane mixture which protects the windings from any airborne contaminants and moisture.

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VPI/VPE Power Transformer

coil-cut2Vacuum Pressure Impregnated (VPI) power transformers utilize an open winding design, where the coil insulation is impregnated with an epoxy resin under vacuum and pressure, providing the windings a degree of protection against moisture and dirt, and improving the thermal conductivity of the winding which reduces localized hot spots. Furthermore, the VPI process removes air voids which deep within the windings, filling them with epoxy instead. These air voids, if not eliminated, can lead to higher partial discharges which can damage the transformer insulation over time, leading to premature failure. For a higher degree of protection, vacuum pressure encapsulated (VPE) coils can be utilized which involves repeated VPI and bake cycles

Read more: VPI/VPE Power Transformer

Cast Coil Power Transformer


Cast coil power transformers feature primary and secondary windings which are vacuum cast inside a solid block of epoxy resin. The epoxy resin is introduced under vacuum in order to penetrate all the spaces within the winding, ensuring a void free casting with minimal partial discharges. The sold casting provides the highest degree of protection to the windings, making them ideally suitable for harsh environmental conditions which include airborne dust & high humidity. Furthermore, the fiberglass reinforcement which is incorporated into the casting provides the transformer with the highest mechanical strength which makes it resilient to short circuit forces.

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Motor Guarding Transient Filter

LineFilters catThe steep voltage wave fronts of the Pulse Width Modulated (PWM) output of Adjustable Frequency Drives (AFD’s) produce high frequency effects which may damage the insulation of motors operated by the equipment. The problems result from two distinct effects.


Read more: Motor Guarding Transient Filter

Air Core Reactor

ir-Core reactors provide a linear impedance with respect to current which is crucial in many applications where an iron core reactor would otherwise saturate.

Read more: Air Core Reactor

Control Power Transformer

Product Overview & Application

CPT webMedium Voltage Control Power Transformers (CPT) are single phase transformers used to supply control power in medium voltage switchgear and transformers. Nominal primary voltages range from 2.4kV to 15kV. The secondary voltage is typically configured for 120/240V (series parallel) operation.

Product Specification

Capacity  500VA to 7,500VA Single Phase
Voltage Class  1.2kV - 15kV (60kV BIL)
Cooling  Self Cooled (ANN / AN)
Frequency  60Hz (50/60Hz Optional)
Conductors  Copper (Cu) Windings
Insulation System  180°C (115°C rise) 
Enclosure Type            Open Construction With Encapsulated Coil
Warranty  12 Months (See Warranty and Limitations)
Quality System  ISO 9001:2015 Quality Management System
  • CSA Certified
  • UL Listed
Reference Standards
  • CSA C22.2 No 47
  • CSA C22.2 No 66.1
  • CSA C9
  • IEEE C57.13.2
Optional Features & Accessories
  • Suitable For 50Hz Nominal Frequency
  • Primary Fuse clips

Drive Isolation Transformer

transformerDrive Isolation Transformers are designed for supplying power to SCR (Silicon Control Rectifier) motor drives which provide convenient variable speed motor control and can save on energy. Unfortunately, the drawback of these variable frequency drives (VFD) is that they produce harmonic voltage distortion and draw harmonic currents from the source which can be damaging both to the transformer supplying the power, and the other equipment that is connected to that supply.


Read more: Drive Isolation Transformer

Hazardous Location Transformer

Product Overview & Application

“Hazardous Locations and Harsh Industrial Environments” typically refers to areas which may contain dangerous and corrosive, explosive or combustible gasses, liquids, or dusts. Typical applications include the mining, petrochemical, and pulp and paper industries. Rex Power Magnetics has been designing and producing a line of dry type transformers for Hazardous Locations and Harsh Industrial Environments. Rex’s product offering in this category includes three varieties, known as the HLA, HLB & HLC product lines, which are CSA and UL approved for CLASS I, DIVISION 2, GROUPS A, B, C, & D.

  • Group A: Atmospheres containing acetylene;
  • Group B: Atmospheres containing butadiene, ethylene oxide, hydrogen (or gases of vapours equivalent in hazard to hydrogen, such as manufactured gas) or propylene oxide
  • Group C: Atmospheres containing acetaldehyde, cyclopropane, diethyl ether, ethylene, hydrogen sulphide, or unsymmetrical dimethyl hydrazine (UDHM), or other gases or vapours of equivalent hazard
  • Group D: Atmospheres containing acetone, acrylonitrile, alcohol, ammonia, benzene, benzol, butane, ethylene, dichloride, gasoline, hexane, isoprene, lacquer solvent vapours, naphtha, natural gas, propane, propylene, styrene, vinyl acetate, vinyl chloride, xylenes, or other gases or vapours of equivalent hazard

*NEW* A variant of Rex’s HLA & HLB transformers is available with IECEx approved CLASS 1 Zone 2 certification. Please contact our sales office for more information on IECEx approved transformers CLASS I, ZONE 2, GROUPS IIA, IIB, IIC — IECEx CSA 13.0011X

  • Group II A: Atmospheres containing acetaldehyde, acetone, cyclopropane, alcohol, ammonia, benzene, benzol, butane, ethylene, dichloride, gasoline, hexane, isoprene, lacquer solvent vapours
  • Group II B: Atmospheres containing acrylonitrile, butadiene, diethyl ether, ethylene, ethylene oxide, hydrogen sulphide, propylene oxide, or unsymmetrical dimethyl hydrazine (UDHM), or other gases or vapours of equivalent hazard
  • Group II C: Atmospheres containing acetylene, carbon disulphide, or hydrogen or other gases or vapours of equivalent hazard

Product Specification

Construction Features
  • ANC design
  • Encapsulated Transformer
  • Bottom/Front Access (based on kVA)
  • Conduit K/O on sides
  • nameplate marking
  • ANC design
  • Encapsulated Transformer
  • Bottom/Front Access (based on kVA)
  • Conduit K/O on sides
  • nameplate marking
  • ANC design
  • Ventilated Transformer
  • Bottom/Front Access (based on kVA)
  • Conduit O/O on sides
Insulation Class  180C  185C  220C
Temperature Rise  115C Maximum  115C Maximum  80C, 115C or 150C
Temperature Code  T3  T3  T3C, T3, or T2C
  • ASA #61 Grey
  • Type 3R outdoor
  • ASA #61 Grey
  • Type 3R outdoor
  • ASA #61 Grey
  • Type 3R outdoor
Certification CSA & UL approved for Class 1, Division2 CSA & UL approved for Class 1, Division2 CSA & UL approved for Class 1, Division2
Application Windings are encapsulated in epoxy, preventing airborne contaminants from reaching the coils, and ths preventing damate to electrical insualtion. As with HLA, the windings are encapsulated. Additionaly, teh connection between the leads and the coils are encapsualted. Wiring to the rest of the system is done at the leads. Conventional construction: non-encapsualted, vented design. Designed to conform to specified temperature code.


K-Factor Rated Transformer

Today's modern electronic, electric components and circuitry such as computers, copiers, printers, fax machines and display terminals utilize switching mode power supplies for their operation. These switching mode power supplies are non-linear in nature and unlike a linear load which uses current from the power source continuously over the sinusoidal cycle, a non-linear load draws current in pulses from the power source thereby creating harmonic distortion. These harmonics currents cause significant power system problems such as:

  • Circuit breakers and fuses blowing far below current ratings
  • Neutrals in transformers and panel boards are much hotter than their ratings
  • Distributions Transformers are overheating even when operating well within their specified nameplate rating

Read more: K-Factor Rated Transformer

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International Reps

International Sales Representatives


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